1. Field of the invention
This invention relates in general to power cables for electrical submersible pumps, and in particular to a flat power cable having an auxiliary line for other uses.
2. Description of the Prior Art
In an electrical submersible pump installation for an oil well, the pump is driven by a downhole AC motor. The downhole pump assembly is suspended on the end of a string of tubing. A power cable extends from the surface alongside the tubing down to the motor.
Two types of power cable are in general use. Each type utilizes three insulated conductors for transmitting three-phase AC power. In one type, the insulated conductors are assembled in a cylindrical or round configuration, each 120 degrees apart from the other and located within an elastomeric jacket. An outer armor comprising a metal strip wraps helically around the round configuration of the jacket.
In the other type of cable, the conductors are assembled in a flat configuration. The conductors are located side by side, touching each other, and with their axes in a common plane. An armor comprising a metal strip wraps helically around the assembled insulated conductors. Flat cable is particularly used where there is insufficient clearance for round cable.
In some installations, an auxiliary line is useful. The auxiliary line might comprise a conductor or electrical wire for transmitting electrical or electronic signals to the surface from a pressure and/or temperature monitor at the downhole pump. Electrical wire could be used for other purposes, such as energizing solenoids for various functions. An auxiliary line could also be used for conveying fluids. It could be used to transmit a cooling fluid from the surface to the motor. It could be used to change the lubricating oil in the motor without pulling the assembly. Chemicals for inhibiting corrosion and scale could be pumped down the auxiliary line.
In the prior art, auxiliary lines have been separately deployed and strapped to the power cable at various points. This subjects the auxiliary line to being damaged during the installation and retrieval process. Separate deployment requires an additional reel, and possibly other surface equipment and personnel to run the line. Auxiliary lines have been proposed to be incorporated within the armor of round cable in U.S. Pat. No. 3,603,718, Gedenk, Sep. 7, 1971.